The present invention relates to linear actuators and to vehicle occupant protection systems or other safety systems employing linear actuators to elevate a vehicle surface such as a hood, in the event of collision or impact with a pedestrian.
Exemplary linear actuators typically employ pyrotechnic means to activate a piston within an actuator. U.S. Pat. No. 6,568,184 exemplifies known pyrotechnic actuators and is herein incorporated by reference in its entirety. The pyrotechnic means typically include an initiator or igniter, and a gas generating composition ignitable by the igniter once the actuator is activated. The use of a gas generating composition in addition to the igniter increases the cost of manufacture given that the gas generating composition must also be manufactured prior to insertion within the actuator. It has been found that because of a “blow-by” or sealing concern between the pyrotechnic means and a first end of an associated piston, it has been necessary to include the gas generating composition to increase the compressive pressure on the igniter side of the piston to ensure piston movement when the actuator is operative. Further, shipping and handling may be more complex or complicated due to transportation and related regulatory requirements related to the shipping of the gas generating composition. It would be an improvement to provide an alternative to the typical pyrotechnically actuated pistons.